This invention relates to a new class of derivatives of 2-thiazoline and of 2-oxazoline presenting an antidotal action towards non-selective herbicides in large-scale agrarian cultivations. Furthermore, the invention relates to a method of defending agrarian cultivations against the toxic action of non-selective herbicides, consisting in administering the captioned compounds to the cultivations, and to the compositions of agrarian use containing said compounds.

It is known that the herbicides belonging to the classes of chloroacetanilides, thiolcarbamates, triazines, etc. are useful compounds in the fight against the infesting plants of important agrarian cultivations.

However, many such herbicides also exert their toxic action towards certain useful cultivations, such as, for example, maize and sorghum, and by consequence, since they are non-selective, they cannot be used for killing weeds infesting such cultivations.

The availability of antidotes, i.e. of compounds which defend the useful cultivations against the action of the herbicides without simultaneously the herbicidal activity towards infesting plants, permits to use these herbicides also for protecting those useful cultivations which would otherwise be damaged.

Among the main herbicides which prove phytotoxic for certain useful cultivations may be cited those belonging to the class of the chloroacetanilides, which includes, for example, N-methoxymethyl-2,6-diethyl-chloroacetanilide (common name: Alachlor), N-butoxymethyl-2,6-diethyl-6-allyl-chloroacetanilide (item M8669), and those belonging to the class of the thiolcarbamates, which includes for example N,N-diisopropyl-S-(2,3-dichloroallyl)-thiolcarbamate (common name Triallate); N,N-diethyl-S-(4-chlorobenzyl)-thiolcarbamate (common name Benthiocarb); N,N-dipropyl-S-ethyl-thiolcarbamate (common name Eptam).

Compounds are known belonging to various chemical classes, which are capable of protecting useful cultivations against the toxic action of herbicides. For example, dichloroacetamides useful as antidotes have been described in US patent n° 4 021 224 (Stauffer) and in US patent n° 4 228 101 (Montedison).

The Applicant's research has now revealed a new class of antidotes -which is the object of the present invention- consisting of the compounds having the general formula (I):

wherein:

• X = S, 0;
• Y = alkyl C₁-C₄ substituted by one or more halogen atoms (Cl, Br, F);
• R¹, R², R3 and R⁴, similar to or different from one another, are hydrogen, alkyl C1-C4.

The toxic action of non-selective herbicides, belonging, for example, to the class of chloroacetanilides and of thiolcarbamates, towards useful cultivations can be highly reduced or eliminated without simultaneously suppressing the herbicidal action towards infesting plants, if the compounds of formula I are utilized as antidotes.

Thus, a further object of the present invention consists in a method of reducing the damage towards useful plants caused by non-selective herbicides belonging, e.g. to the class of the chloroacetanilides or of the thiolcarbamates, such method consisting in treating the plants or the soil in which they grow with an effective amount of an antidote of formula I, either as such or as a suitable composition.

Another object of this invention is represented by compositions containing a compound of formula I as an active ingredient besides inert carriers and optionally herbicides and other additives, useful for treating the seeds of useful plants, the plants themselves or the soil in which they grow.

A further object of the present invention are the seeds of useful plants when treated with an effective amount of a compound of formula I.

The compounds of formula I are prepared according to general methods adopted in the synthesis of 2-thiazolines. For example, it is possible to utilize the Ritter reaction between a nitrile and a diol or a 2-mercapto-alcohol (Organic Reactions, vol. 17 (1969), 237) according to the following equation:

wherein X, Y, R¹, R², R³ and R⁴ are the same as defined hereinabove.

In particular, when X = 0, the compounds of formula (I) can also be obtained by reacting a haloid salt of a 2-halo-alkylamine with the proper anhydride (Gabriel, B.22, 2221) according to the equation:

Furthermore, in particular, when X = S, the compounds of formula (I) can be obtained by reacting a disulphide of a 2-mercaptoalkylamine with the proper anhydride (Gabriel, B.24, 1117) according to the equation:

Similarly, another general method which is very useful for synthetizing the compounds (I) in which X = S, consists in treating a nitrile with a 2-mercaptoalkylamine according to the equation:

This reaction can be carried out in a suitable alcoholic solvent, for example methanol or ethanol, in reflux conditions.

As mentioned hereinbefore, the antidotes of formula (I) exert a remarkable antidotal action which is much higher than that of antidotes of the prior art, for example, much higher than the action of the antidote N,N-diallyldichloroacetamide (R-25788) described in the above- cited US patent n° 4 021 224 (comparative example n° 4).

The antidotes of formula (I) can be applied to the useful cultivations according to different methods. For example, they can be utilized for a preventive dressing of the seeds, so that the plant which will develop from said seeds may be protected against the toxic action of non-selective herbicides. As an alternative, the compounds of formula (I) can be used for treating the plant itself or the soil in which it grows. In this case, the antidotes can be distributed either alone or preferably combined with the non-selective herbicide.

The various kinds of application require different conditions which influence the practical aspects of the treatment, such as antidote amount, treatment period and type of composition.

Other factors influencing the practical aspects of the treatment are the type of cultivation to be protected, the non-selective herbicide which is used, climatic and environmental conditions.

When the antidote is utilized in a preventive dressing of the seeds, it can be utilized as such or preferably in the form of a suitable composition.

The compositions for the dressing of the seeds may be in the form of powders, wettable powders or emulsifiable concentrates and generally consist of the active compounds in amounts ranging from 0.5 to 95% by weight and of the usual inert carriers which, depending on the type of composition, may be solid, such as talc, silica, diatomaceous earth, bentonite, alkyl-aromatic hydrocarbons, acetone, cyclohexanone and mixtures thereof.

Proper additives, such as surfactants, wetting agents, dispersants and mixtures thereof can also be present in the compositions.

A specific example of a composition in powder form for the seed dressing in the following:

Some examples of useful wetting agents are polyoxy-ethylated nonyl-phenols, sodiumalkylnaphtalensulphonates, sodium alkylsulpho- succinates; some examples of dispersants are lignosulphonates of sodium, calcium or aluminium, sodium alkylnaphtalensulphonates condensed with formaldehyde, maleic anhydride/diisobutylene copolymers; some examples of adhesion-promoting agents are glycols, glycerine, polyglycols, arabic gum, starch, sodium polymethacrylate with different molecular weights.

All these additives are well known in the formulative field and are commercially also available in already prepared mixtures.

The above-mentioned compositions are prepared by mixing the ingredients and by homogenizing them by means of grinding until the desired particle size is obtained.

Such compositions may be used as such for the dry seed-dressing, or may be diluted with water for wet seed-dressing.

As indicated hereinabove, the antidote amount to the distributed onto the seeds varies as a function of various factors; however, it is generally sufficient to use product amounts ranging from 0.1 to 100 g/kg of seed.

Of course, the treatments carried out directly on the plant or in the medium in which it grows require use of the antidote in the form of a suitable composition according to common practice for this kind of application.

In the applications in which the antidote is distributed onto the vegetation or in the soil along with the non-selective herbicide in a single formulation, the type of formulation and the content vary both in relation to the facts disclosed hereinbefore and in relation to the type of herbicide utilized and to the characteristics thereof.

The antidote amount to be utilized generally ranges from 0.03 to 10 parts by weight per 100 parts by weight of herbicide.

Among the cultivations which can be defended against the toxic action of non-selective herbicides due to the use of antidotes of formula (I), other than maize, may be cited beet, sorghum and wheat.

In order to better illustrate the present invention, the following examples are given.

EXAMPLE 1

Preparation of 2-trichloromethyl-2-thiazoline (compound N° 1).

5.65 g (0.05 moles) of 2-mercaptoethylamine hydrochloride and 7.2 g (0.05 moles) of trichloroacetonitrile in 50 ml of methanol were heated at reflux during 3 hours. At the end of this step, the solvent was distilled off under reduced pressure and the residual oil was diluted with 100 ml of diethylether.

The ammonium chloride which had formed during the reaction was separated by filtration and the ethereal solution, after washing with water, drying with Na₂S0₄ and evaporation of the solvent, provided 9 g (0.044 moles) of the product to be obtained, in the form of a liquid having a boiling point of 95-100°C (20 mm HG). ^I.R.: γ (^C=N) ¹⁶¹⁵ cm-1.

EXAMPLE 2

Preparation of 2-dichloromethyl-2-thiazoline (M13302) (compound N° 2)

Starting from dichloroacetonitrile and by means of a process analogous to that described in example 1, the compound indicated in the title and having the following characteristics was prepared:

• Physical state: pale-yellow oil,
• I.R.: γ (C=N) 1620 cm-¹.
• 1H-NMR (CDC1₃)

• δ (ppm): H 3.48 (2H, triplet, J = 8 Hz)
• H_b 4.36 (2H, triplet, J = 8 Hz)
• H_c 6.52 (1H, singlet).

EXAMPLE 3

Determination of the antidotal activity for treatment of the soil. The test was carried out on maize of variety known as Decalbe XL 72 A, properly sowed into pots containing sandy soil. The sowed pots were divided into three groups. One group was treated by spraying the soil with a composition containing the herbicide Eptam (in a quantity corresponding to 8 kg/ha of active substance), to which the compound of formula (I) to be tested and used at the selected concentration was added; a second group (control) was treated with the herbicide only while the third group was treated neither with the herbicide nor with the antidote and was used as a check.

The pots were kept in a conditioned room (spring-growth conditions) at 15-24°C, 70% of relative humidity, 12-hour photoperiod, and were regularly sprinkled to secure a good germination.

10 days after treatment, the antidotal activity was evaluated by comparing the plant and the vegetative state thereof with the plants treated with the herbicide only and with those not treated at all.

The results were expressed on the basis of the plant's vegetative state according to a scale of values ranging from 4 (complete stop of the growth or death of the plant) to 0 (sound plant, growth like that of the check grown in the absence of both herbicide and antidote). Consequently a numerical evaluation like that of the plants treated with the herbicide only indicates the absence of the antidotal effect, and an evaluation equal to zero indicates full protection of the plant against the toxic action exerted by the herbicide; the intermediate values indicate a partial antidotal effect, increasing towards the lower values.

Preliminary laboratory tests indicated that the antidotes of formula (I) are not toxic towards maize, and that the herbicidal activity of Eptam towards the common infesting plants of Maize (Solanum nigrum, Amarantus spp., Echinochloa spp., Digitaria spp., Setaria spp., Sorghum halepense, Panichum dichotomiflorum, Cyperus rotundus and Cyperus esculentus) is not affected by the presence of the antidote in this kind of test.

The compounds of examples 1 and 2 (N° 1 and N° 2 respectively) exhibited a full antidotal activity (growth of the plant equal to the one of the check, evaluation = 0) at a dose of 400 g/ha (5% by weight in respect of the herbicide), while in the absence of the antidote, the herbicide Eptam, at the considered quantity caused a complete halt in the plants' development (evaluation = 4).

EXAMPLE 4

Determination of the antidotal activity of Compound n° 2 at various doses for treatment of the soil in the defence of maize.

Following the same steps described in example 3, but using increasing quantities of the compounds being tested, the results recorded in the following Table and expressed as % of defence against the phytotoxic action of Eptam were obtained.